Regulation of artery, immune and nervous systems by albutensin derived from serum albumin

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1. Bovine albutensin A (Ala-Leu-Lys-Ala-Trp-Ser-Val-Ala-Arg) was isolated from the tryptic digest of bovine serum albumin as an ileum-contracting peptide. Human and porcine counterparts (Ala-Phe-Lys-Ala-Trp-Ala-Val-Ala-Arg and Ala-Phe-Lys-Ala-Trp-Ser-Leu-Ala-Arg) were also ileum-contracting peptides. These peptides were agonists for complement C3a and C5a. They stimulated phagocytosis and induction of TNF.2. Bovine albutensin C (Arg-His-Pro-Glu-Tyr-Ala-Val-Ser-Val-Leu-Leu-Arg) was also isolated from the tryptic digest of bovine serum albumin as an ileum-contracting peptide. Human and porcine counterparts did not show the same activity. Albutensin C was also an agonist for C3a receptor and stimulated phagocytosis.3. Human albutensin A showed affinity for bombesin receptor (IC_<50>=133muM). This peptide stimulated food intake at a dose of 10nmol (icv.) in fasted mice. However, it suppressed food intake at a dose of 30 nmol. Human albutensin A seems to be a partial agonist for bombesin receptor because bombesin suppress food intake. On the other hand, synthetic human des-Arg-albutensin A-NH_2 also showed affinity for bombesin receptor and supressed food intake at 100 nmol. It didn't stimulate food intake and seems to be a bombesin agonist. Bovine and porcine albutensin A did had no effect on food intake because their affinities for bombesin receotor were low.4. A synthetic fragment peptide of bovine serum albumin, Tyr-Leu-Ser-Leu-Ile-Leu-Asn-Arg showed affinity for neuropeptide Y_2 receptor. This peptide was named albutensin B.Albutensin might be an antagonist for neuropeptide Y because it suppressed food intake in fasted mice after icv.